PIDTC PILOT/FEASIBILITY CORE SUMMARY/ABSTRACT The Primary Immune Deficiency Treatment Consortium (PIDTC) was established in 2009 as a collaboration among North American centers with expertise in treating infants and children with rare, but serious primary immunodeficiencies (PIDs). In this application, we propose a clinical research project examining a group of newly described disorders, the Primary Immune Regulatory Disorders (PIRD, Project 6906), which extends the scope of PIDTC to encompass genetic disorders affecting immune regulation. The Pilot/Feasibility Core has funded 7 projects in its lifetime, 4 in the past cycle. These annual $50,000 awards are granted after rigorous review for scientific merit, prioritizing projects that have the potential to impact the field, leverage data and infrastructure of the RDCRN and PIDTC, and have a high likelihood of translation to clinical trials. Investigators wishing to receive a 2nd year of funding are reviewed in a competitive renewal process that puts emphasis on demonstration of meeting milestones stated in the application. In this application, we plan to continue our successful and productive Pilot program, transitioning the leadership to Dr. Sung-Yun Pai, to fulfill Specific Aim 1: To select and fund timely innovative research in PID and its treatment which in turn results in tangible outcomes that advance the goals of PIDTC and fuel clinical trial readiness. Notwithstanding our successes to date, we have recognized that implementation of funded Pilot studies using data and samples acquired in the context of the clinical research projects has been slow. For future Pilot projects, we will pursue Specific Aim 2: To use a PIDTC-specific, consortium-wide, biological sampling and sharing protocol to facilitate rapid implementation of Pilot/Feasibility Core supported studies and other studies relying on samples from patients. Through these specific aims, we hope to broaden the success we have had leveraging clinical research protocol and Pilot project data in SCID to develop and launch an evidence-based clinical trial in SCID (Conditioning SCID Infants Diagnosed Early, CSIDE study, NCT03619551) to other PID and PIRD.